Activated hardening of photographic emulsions



United States Patent 3,255 000 ACTIVATED HARDENIhiG 0F PHOTOGRAPHIC EMULSIONS John W. Gates, .lr., and Norman Allentoif, Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Feb. 14, 1963, Ser. No. 258,599 8 Claims. (Cl. 96111) This invention relates to the activated hardening of photographic emulsions in which a hardener having a double bond in the alpha position to an oxygen containing group such as an acid, ester, amide, carbonyl or sulfonyl group is incorporated in a gelatin photographic emulsion which emulsion is then coated out onto a support in the form of a photosensitive layer and applied thereover is a layer containing a volatile organic base.

Oftentimes photographic gelatin emulsions contain hardeners whose action is prolonged over a considerable period of time; hence, an emulsion layer having the desired degree of hardness when freshly made may continue to harden, upon keeping, to such a degree that it loses its permeability to processing solutions. This may result in undesirable sensitometric effects such as greatly decreased contrast after storage.

One object of our invention is to provide for the hardening of photographic emulsion layers in which the desired degree of hardness is attained in the fresh coating and the full effect of the hardener is obtained initially rather than continuing over a prolonged period. Another object of our invention is to provide for a practical application of a hardening accelerator to photographic emulsions containing hardeners which have a double bond in the alpha position to an oxygen containing group such as an acid, ester, amide, carbonyl or sulfonyl group therein. A further object of our invention is to avoid the.

deleterious effects obtained by adding hardening accelerators directly to photographic emulsions. Other objects of our invention will appear herein.

We have found that the above objects are accomplished by incorporating in a gelatin-silver halide photographic emulsion as a hardener a compound having a double bond in the alpha position to an oxygen containing group such as an acid, ester, amide, carbonyl or sulfonyl group and after this emulsion has been applied as a layer on a suitable support it is then overcoated With a subsequent layer containing a volatile organic base followed by drying which removes the organic base from the coated layers. Examples of hardeners of the type described which are useful in our invention are 1,3,5-triacryloylhexahydro-s-tri-azine, divinyl sulfone, acryloxyethylcarbamyl-substituted gelatin, N-methylolacrylamide, 3,5- cyclopentenedione, the copolymers of ethylene and betavinylsulfonylethyl acid maleate and the copolymers of vinylacryloxyethylurethane and vinyl acid succinate. Examples of volatile organic bases which may be employed are any of the amines which have a boiling point of up to about 125 C. so as to be readily removed inthe drying operations in the manufacture of the photographic film. Suitable examples of such amines are sec.-butylamine, diethylamine, n-butylamine, n-pentylamine, di-isopropylamine, di-n-propylamine, N-ethylbutylamine, N- methyl-di-propylamine, N-methylbutylamine and triethylamine.

Any amount of the hardener incorporated in the photographic emulsion has some hardening effect but in practice ordinarily 0.25 to 25.0% of the hardener based on the weight of the colloid is employed for optimum results. The amount of volatile organic base employed in the overcoating operations should be such that the layer has a decided basicity such as a pH of 812 or more. The emulsion is coated onto any one of the conventional types 3,255,969 Patented June 7, 1966 of film supports such as cellulose tr-iacetate or polyester film base or paper it being understood that the support may be subbed or otherwise coated in conventional manner before the application of the emulsion layer. After the emulsion layer is applied and preferably after drying, it is then coated with an aqueous overcoat containing the volatile organic base which is then dried in the usual manner. The temporary contacting of the emulsion layer with the alkaline overcoat is sutficient to cause accelerated hardening even though the base is removed shortly after the overcoating is applied during the normal drying process.

The following examples illustrate our invention:

Example 1 A fast negative silver bromoiodide-gel-atin emulsion containing as a hardener 2.0%' of 1,3,5-triacryloylhexahydro-s-triazine based on the weight of the gelatin was coated onto a cellulose triacetate film. support at the rate of 840 mg. of gelatin per square foot. Hardeners of this type are described in Belgian Patent No. 575,428. The emulsion coating was then dried.

Another coating of emulsion was applied to like support in the same manner but immediately after drying TABLE I Fresh Tests Optical Ctg. N0. Density Vert. 120 F. Swell 1 week Rel incubation Speea 7 Fog Wet Dry 7 100 l. 20 0.01 2. l2 1. 98 177 0. 9O 91 l. 05 0. 02 1. 76 1. 88 0. 87

The vertical. swell in water was determined by immersing the film in water and measuring the percent of thickness increase of the coating on the film base. The coating in which a triethylamine overcoating was used showed a great increase in 'ha-rdness as compared to the coating without the triethylamine overcoat. This eifect is also demonstrated by the lower gamma of the second Example 2 A coating was applied to a support from the same kind of emulsion as used in the preceding example except that 15.0% of hardener based on the weight of the gelatin was used. The hardener employed was acryloxyethylcarbamy-l-substituted gelatin having the structural formula:

H II gelatin-C NHC H20 H20 0 C H=CH1 A second coating of the emulsion was made in like manner and after drying it was overcoated with triethylamine as described in the preceding example. The films obtained were exposed, processed, fixed, Washed and dried in the manner described in the preceding example. Two

additional coatings were made using emulsion containing no hardener and emulsion with no hardener but overcoated with aqueous triethylamine. The resulting products were designated A, B, C and D, respectively. The results obtained on testing these 4 film samples were as It is apparent that the t-riethylamine overcoat alone (Ctg. No. D) caused no more than a relatively insignificant reduction of the very large vertical swell in the case of the unhardened coating (Ctg. No. C). Also it is apparent that the triethylamine treatment causes no deleterious photographic efiects on the film (C'tg. No. B) which is treated therewith. V

While particular reference has been made to gelatin as the colloid in the photographic silver halide emulsion, any vehicle which contains amino groups and which is compatible with the silver halide may be used.

The photographic emulsions of our invention may contain, if desired, the usual coating aids, sensitizers, stabilizers, etc. as are known in the art.

If desired, the photographic emulsion and the fluid containing the volatile organic base may be applied simultaneously by the method described in T. A. Russell US. Patent 2,761,418.

We claim:

1. A method for the activated hardening of photographic emulsion layers which comprises incorporating in a silver halide-gelatin photographic emulsion a hardening amount of l,3,5-triacryloylhexahydro-s-triazine, applying the emulsion to a support therefor and after drying the resulting layer applying thereover a layer containing triethylamine.

2. A method for the activated hardening of photographic emulsion layers Nvhich comprises incorporating in a silver halide-gelatin photographic emulsion a hardening amount of acryloxyethylcarbamyl-substituted gelatin,

. coating the emulsion onto a support and after drying the 6 the emulsion has been apphed to the support and the resulting layer has been dried applying thereover a layer containing an organic base having a boiling point of no more than approximately 125 C,

4. A method for the activated hardening of photographic emulsion layers which comprises incorporating in the emulsion to be coated onto a support a hardener for the vehicle thereof comprising a compound characterized by the presence of a double bond alpha to ,a carbonyl or a sulfonyl of an acid, ester or amide radical which contains a carbonyl, a sulfonyl or both and after the emulsion has been applied to the support and the resulting layer has been dried applying thereover a layer containing triethylamine.

5. A method for the activated hardening of photographic emulsion layers which comprises incorporating in a silver halide-gelatin emulsion a gelatin hardener characterized by the presence therein of a double bond alpha to a carbonyl or .a sulfonyl of an acid, ester or amide radical which contains a carbonyl, a sulfonyl or both, applying the emulsion to a support and after drying the resulting layer applying thereover a layer containing an organic base having a boiling point of no more than approximately C.

6. A method for the activated hardening of photographic emulsion layers which comprises incorporating in a silver halide-gelatin emulsion a gelatin hardener characterized by the presence therein of a double bond alpha to a carbonyl or a sulfonyl of an acid, ester or amide radical which contains a carbonyl, a sulfonyl or both, applying the emulsion to a support and after drying the resulting layer applying t'hereover a layer containing triethylamine.

7. In the preparation of photographic products in which a photographic emulsion containing a hardener for the vehicle thereof is a compound characterized by the presence of a double bond alpha to a carbonyl or a sulfonyl of an acid, ester or amide radical which contains a carbonyl, a sulfonyl or both is coated out onto a support and dried, the step which comprises applying over the dry photographic emulsion layer a layer of an organic base having a boiling point of no more than 125 C.

8. A method of preparing photographic products in which a gelatin-silver halide photographic emulsion contains a gelatin hardener which is a compound characterized by the presence of a double bond alpha to a carbonyl or a sulfonyl of an acid, ester or amide radical which contains a carbonyl, a sulfonyl or both, is applied to a support and dried, the step which comprises applying over the dry photographic emulsion layer a layer of triethylamine.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS 10/1960 Germany.

2/1961 Great Britain.

J. TRAVIS BROWN, Acting Primary Examiner.

NORMAN G. TORCHIN, Examiner. J. H. RAUBITSCHEK, Assistant Examiner. 

1. A METHOD FOR THE ACTIVATED HARDENING OF PHOTOGRAPHIC EMULSION LAYERS WHICH COMPRISES INCORPORATING IN A SILVER HALIDE-GELATIN PHOTOGRAPHIC EMULSION A HARDENING AMOUNT OF 1,3,5-TRIACRYLOYLHEXAHYDRO-S-TRIAZINE, APPLYING THE EMULSION TO A SUPPORT THEREFOR AND AFTER DRYING THE RESULTING LAYER APPLYING THEREOVER A LAYER CONTAINING TRIETHYLAMINE.
 2. A METHOD FOR THE ACTIVATED HARDENING OF PHOTOGRAPHIC EMULSION LAYERS WHICH COMPRISES INCORPORATING IN A SILVER HALIDE-GELATIN PHOTOGRAPHIC EMULSION A HARDENING AMOUNT OF ARYLOXYETHYLCARBAMYL-SUBSTITUTED GELATIN, COATING THE EMULSION ONTO A SUPPORT AND AFTER DRYING THE RESULTING LAYER APPLYING THEREOVER A LAYER OF TRIETHYLAMINE.
 3. A METHOD FOR THE ACTIVATED HARDENING OF PHOTOGRAPHIC EMULSION LAYERS WHICH COMPRISES INCORPORATIG IN THE EMULSION TO BE COATED ONTO A SUPPORT A HARDENER FOR THE VEHICLE THEREOF COMPRISING A COMPOUND CHARACTERIZED BY THE PRESENCE OF A DOUBLE BOND ALPHA TO A CARBONYL OR A SULFONYL OF AN ACID, ESTER OR AMIDE RADICAL WHICH CONTAINS A CARBONYL, A SULFONYL OR BOHT AND AFTER THE EMULSION HAS BEEN APPLIED TO THE SUPPORT AND THE RESULTING LAYER HAS BEEN DRIED APPLYING THEREOVER A LAYER CONTAINING AN ORGANIC BASE HAVING A BOILING POINT OF NO MORE THAN APPROXIMATELY 125*C.
 4. A METHOD FOR THE ACTIVATED HARDENING OF PHOTOGRAPHIC EMULSION LAYERS WHICH COMPRISES INCORPORATING IN THE EMULSION TO BE COATED ONTO A SUPPORT A HARDENER FOR THE VEHICLE THEREOF COMPRISING A COMPOUND CHARACTERIZED BY THE PRESENCE OF A DOUBLE BOND ALPHA TO A CARBONYL OR A SULFONYL OF AN ACID, ESTER OR AMIDE RADICAL WHICH CONTAINS A CARBONYL, A SULFONYL OR BOTH AND AFTER THE EMULSION HAS BEEN APPLIED TO THE SUPPORT AND THE RESULTING LAYER HAS BEEN DRIED APPLYING THEREOVER A LAYER CONTAINING TRIETHYLAMINE. 